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heat n glo CO spillage AFTER new glass/seal

Had over 200PPm CO spillage on a Heat N Glo GDV 5000. It had the silicone gasket, most of which was missing, so ordered a new glass with rope type gasket.

Installed new glass and now have 5-10PPM spillage around one side only.
Pulled and checked glass, gasket, and insert for issues - nothing obvious, no bent metal, missing gasket, old gasket material stuck on unit. Wing nuts are tight and I tried with and without rubber on brackets.

I have done smoke bomb tests to find the leaks. Most heating suppliers have 1 minute smoke bombs. All you need is a 30 second smoke bomb but buy a couple as they are only a few bucks each. The last one I did showed leaks in 4 places. Place it in with the wick on the main burner to lite the wick and close the glass back up so it should be sealed to the inside of the house. Also have a glass of water handy to drizzle on it afterward. Get ok from Cust that it may smell temporarily. You will have to clean the glass afterward. I practiced on my home fireplace first and it only can be done on direct vent units. Be prepared to shut down the unit and condemn it if it leaks at factory sealed joints. Good Luck

Almost forgot, you can also try the "Paper Test" where you try and slide the corner of a piece of paper behind the gasket in between the gasket and fireplace opening. If you can slide it in you know the seal isn't great. I had a GTI that had a slight bow to the fireplace and wouldn't seal, had the same red silicone gasket. I actually still have the glass after replacing the unit.

testing fireplace seals

First verify it was properly installed and firing. Inspect the venting inside and out. On a cold unit, puff the perimeter of the glass with a chemical smoke puffer. Puff the penetrations for pilot tubing and igniter, and gas train. Breaches in the gasket will allow smoke to enter the firebox. If you see smoke behind glass, you've found a leak. Remove the glass and look at the footprint. Is there discoloration in one place where heat has affected the powder coating/ paint? Re-seal and fire unit. Hold tip of pump-type combustion analyzer within 1" of glass and check for CO. Hold probe at floor and look for falling O2, which indicates CO2 displacing the O2.

If the unit is dirty, you can get low levels of CO from cooking dust and oils. Clean the unit with a citrus based solvent cleaner.